The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft is moved by several turbojet engines each housed in a nacelle accommodating a set of auxiliary actuation devices associated with the operation thereof and ensuring various functions when the turbojet engine is operating or shut down.
In particular, these auxiliary actuation devices comprise a thrust reverser mechanical system.
A turbojet engine nacelle generally has a substantially tubular structure comprising an air inlet upstream of the turbojet engine, a median section intended to surround a fan of said turbojet engine, a downstream section intended to surround the combustion chamber of the turbojet engine and possibly integrating thrust reversal means, and is generally ended by an ejection nozzle the outlet of which is located downstream of the turbojet engine.
Modern nacelles are intended to accommodate a bypass turbojet engine capable of generating through the blades of the rotating fan, a hot air flow (primary flow) and a cold air flow (secondary flow) which flows outside the turbojet engine through an annular passage, also called flow path formed between a fairing of the turbojet engine and an inner wall of the nacelle. The two air flows are ejected from the turbojet engine through the rear of the nacelle.
The role of a thrust reverser is, during the landing of an aircraft, to improve the braking capacity thereof by redirecting forward at least one portion of the air ejected from the turbojet engine. In this phase, the thrust reverser obstructs at least one portion of the flow path of the cold flow and directs this flow forward of the nacelle, thereby generating a counter-thrust which is added to the braking of the wheels and the air brakes of the aircraft.
Generally, the structure of a thrust reverser comprises a thrust reverser cowl which can be displaced between, on the one hand, a reverse jet position in which it opens in the nacelle, a passage intended for the diverted air flow, and on the other hand, a direct jet position in which it closes this passage.
In the case of a thrust reverser with cascade vanes, the reorientation of the air flow is performed by the cascade vanes, associated with thrust reverser flaps blocking at least partially the air flow path, the cowl having only a simple sliding function aiming to uncover or cover these cascade vanes.
In turn, the thrust reverser flaps, also called blocking flaps are activated and driven by the sliding of the movable cowl until obstructing at least partially the flow path downstream of the cascade vanes, so as to optimize the reorientation of the cold air flow.
In a known manner, the cascade vanes are mounted on a front frame serving as a fixed portion of the thrust reverser device and attached to a casing of the fan of the turbojet engine. This front frame also ensures the support for the actuating cylinders of the movable cowls.
Besides participating in a thrust reversal function, as it belongs to the rear section of the nacelle, a movable thrust reverser cowl includes de facto a downstream portion forming the ejection nozzle.
The section of the ejection nozzle can be adapted depending on the different phases of flights, namely, in particular the takeoff, climb, cruise, descent and landing in order to always maintain an optimal nozzle section depending on the turbojet engine speed. The nozzle will be therefore called variable nozzle.
Such a variable nozzle is associated with an actuation system enabling this section variation.
There are several solutions to realize a variable nozzle.
A first solution is to provide pivoting end flaps mounted on the movable thrust reverser cowl and the pivoting of which results in an increase or a reduction of the outlet section. Such a system is described in particular in the documents FR 2 929 998 and FR 2 934 326.
There are also known panels movably mounted in translation inside the movable thrust reverser cowl, telescopically, the backward movement or retraction of which similarly causes the increase or the reduction of the outlet section.
In the case of a thrust reverser provided with a variable section nozzle, it is known to actuate the deployment of the movable cowl and the variation mechanism of the variable nozzle by the same cylinders, the movable cowl and the variable nozzle being coupled and uncoupled by a coupling device.
This coupling device selectively and rigidly connects the cowl and the variable nozzle, the variable nozzle being free when the cowl is locked on the structure of the thrust reverser in the direct jet position, and the variable nozzle being coupled on the cowl when the cowl is unlocked, so that the nozzle and the cowl are simultaneously driven in displacement.
In general, this type of coupling device is relatively complex and often requires an alignment of different parts in order to enable the coupling of the cowl and the variable nozzle.
The high number of parts of this type of coupling device can be a source of failure and often leads to an average reliability.
In addition, the coupling and uncoupling jerks are not damped and may lead to disadvantageous constraints in terms of wear and reliability of the mechanical parts.